<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
a	O
project	B-Application
fork	I-Application
happens	O
when	O
developers	O
take	O
a	O
copy	O
of	O
source	O
code	O
from	O
one	O
software	B-Architecture
package	I-Architecture
and	O
start	O
independent	O
development	O
on	O
it	O
,	O
creating	O
a	O
distinct	O
and	O
separate	O
piece	O
of	O
software	B-Application
.	I-Application
</s>
<s>
The	O
term	O
often	O
implies	O
not	O
merely	O
a	O
development	B-General_Concept
branch	I-General_Concept
,	O
but	O
also	O
a	O
split	O
in	O
the	O
developer	O
community	O
;	O
as	O
such	O
,	O
it	O
is	O
a	O
form	O
of	O
schism	O
.	O
</s>
<s>
Grounds	O
for	O
forking	O
are	O
varying	O
user	O
preferences	O
and	O
stagnated	O
or	O
discontinued	O
development	O
of	O
the	O
original	O
software	B-Application
.	I-Application
</s>
<s>
Free	B-License
and	I-License
open-source	I-License
software	I-License
is	O
that	O
which	O
,	O
by	O
definition	O
,	O
may	O
be	O
forked	O
from	O
the	O
original	O
development	O
team	O
without	O
prior	O
permission	O
,	O
and	O
without	O
violating	O
copyright	O
law	O
.	O
</s>
<s>
However	O
,	O
licensed	O
forks	B-Language
of	O
proprietary	B-Application
software	I-Application
(	O
e.g.	O
</s>
<s>
Unix	B-Application
)	O
also	O
happen	O
.	O
</s>
<s>
The	O
word	O
"	O
fork	B-Language
"	O
has	O
been	O
used	O
to	O
mean	O
"	O
to	O
divide	O
in	O
branches	O
,	O
go	O
separate	O
ways	O
"	O
as	O
early	O
as	O
the	O
14th	O
century	O
.	O
</s>
<s>
In	O
the	B-Application
software	I-Application
environment	O
,	O
the	O
word	O
evokes	O
the	O
fork	B-Language
system	O
call	O
,	O
which	O
causes	O
a	O
running	O
process	O
to	O
split	O
itself	O
into	O
two	O
(	O
almost	O
)	O
identical	O
copies	O
that	O
(	O
typically	O
)	O
diverge	O
to	O
perform	O
different	O
tasks	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
software	O
development	O
,	O
"	O
fork	B-Language
"	O
was	O
used	O
in	O
the	O
sense	O
of	O
creating	O
a	O
revision	O
control	O
"	O
branch	B-General_Concept
"	O
by	O
Eric	O
Allman	O
as	O
early	O
as	O
1980	O
,	O
in	O
the	O
context	O
of	O
Source	B-Device
Code	I-Device
Control	I-Device
System	I-Device
:	O
</s>
<s>
The	O
term	O
was	O
in	O
use	O
on	O
Usenet	B-Application
by	O
1983	O
for	O
the	O
process	O
of	O
creating	O
a	O
subgroup	O
to	O
move	O
topics	O
of	O
discussion	O
to	O
.	O
</s>
<s>
"	O
Fork	B-Language
"	O
is	O
not	O
known	O
to	O
have	O
been	O
used	O
in	O
the	O
sense	O
of	O
a	O
community	O
schism	O
during	O
the	O
origins	O
of	O
Lucid	B-Language
Emacs	I-Language
(	O
now	O
XEmacs	B-Language
)	O
(	O
1991	O
)	O
or	O
the	O
Berkeley	B-Operating_System
Software	I-Operating_System
Distributions	I-Operating_System
(	O
BSDs	B-Operating_System
)	O
(	O
1993	O
–	O
1994	O
)	O
;	O
Russ	O
Nelson	O
used	O
the	O
term	O
"	O
shattering	O
"	O
for	O
this	O
sort	O
of	O
fork	B-Language
in	O
1993	O
,	O
attributing	O
it	O
to	O
John	O
Gilmore	O
.	O
</s>
<s>
However	O
,	O
"	O
fork	B-Language
"	O
was	O
in	O
use	O
in	O
the	O
present	O
sense	O
by	O
1995	O
to	O
describe	O
the	O
XEmacs	B-Language
split	O
,	O
and	O
was	O
an	O
understood	O
usage	O
in	O
the	O
GNU	B-Operating_System
Project	O
by	O
1996	O
.	O
</s>
<s>
Free	B-License
and	I-License
open-source	I-License
software	I-License
may	O
be	O
legally	O
forked	O
without	O
prior	O
approval	O
of	O
those	O
currently	O
developing	O
,	O
managing	O
,	O
or	O
distributing	O
the	B-Application
software	I-Application
per	O
both	O
The	B-Application
Free	I-Application
Software	I-Application
Definition	I-Application
and	O
The	B-License
Open	I-License
Source	I-License
Definition	I-License
:	O
</s>
<s>
In	O
free	B-Application
software	I-Application
,	O
forks	B-Language
often	O
result	O
from	O
a	O
schism	O
over	O
different	O
goals	O
or	O
personality	O
clashes	O
.	O
</s>
<s>
In	O
a	O
fork	B-Language
,	O
both	O
parties	O
assume	O
nearly	O
identical	O
code	O
bases	O
,	O
but	O
typically	O
only	O
the	O
larger	O
group	O
,	O
or	O
whoever	O
controls	O
the	O
web	O
site	O
,	O
will	O
retain	O
the	O
full	O
original	O
name	O
and	O
the	O
associated	O
user	O
community	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
a	O
friendly	O
fork	B-Language
or	O
a	O
soft	O
fork	B-Language
is	O
a	O
fork	B-Language
that	O
does	O
not	O
intend	O
to	O
compete	O
,	O
but	O
wants	O
to	O
eventually	O
merge	O
with	O
the	O
original	O
.	O
</s>
<s>
Eric	O
S	O
.	O
Raymond	O
,	O
in	O
his	O
essay	O
Homesteading	O
the	O
Noosphere	O
,	O
stated	O
that	O
"	O
The	O
most	O
important	O
characteristic	O
of	O
a	O
fork	B-Language
is	O
that	O
it	O
spawns	O
competing	O
projects	O
that	O
cannot	O
later	O
exchange	O
code	O
,	O
splitting	O
the	O
potential	O
developer	O
community	O
"	O
.	O
</s>
<s>
David	O
A	O
.	O
Wheeler	O
notes	O
four	O
possible	O
outcomes	O
of	O
a	O
fork	B-Language
,	O
with	O
examples	O
:	O
</s>
<s>
The	O
death	O
of	O
the	O
fork	B-Language
.	O
</s>
<s>
It	O
is	O
easy	O
to	O
declare	O
a	O
fork	B-Language
,	O
but	O
considerable	O
effort	O
to	O
continue	O
independent	O
development	O
and	O
support	O
.	O
</s>
<s>
A	O
re-merging	O
of	O
the	O
fork	B-Language
(	O
e.g.	O
,	O
egcs	O
becoming	O
"	O
blessed	O
"	O
as	O
the	O
new	O
version	O
of	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
.	O
)	O
</s>
<s>
the	O
X.Org	B-Operating_System
Server	I-Operating_System
succeeding	O
and	O
XFree86	B-Device
dying	O
.	O
)	O
</s>
<s>
Successful	O
branching	B-General_Concept
,	O
typically	O
with	O
differentiation	O
(	O
e.g.	O
,	O
OpenBSD	B-Operating_System
and	O
NetBSD	B-Device
.	O
)	O
</s>
<s>
Distributed	B-Protocol
revision	I-Protocol
control	I-Protocol
(	O
DVCS	O
)	O
tools	O
have	O
popularised	O
a	O
less	O
emotive	O
use	O
of	O
the	O
term	O
"	O
fork	B-Language
"	O
,	O
blurring	O
the	O
distinction	O
with	O
"	O
branch	B-General_Concept
"	O
.	O
</s>
<s>
With	O
a	O
DVCS	O
such	O
as	O
Mercurial	B-Protocol
or	O
Git	B-Application
,	O
the	O
normal	O
way	O
to	O
contribute	O
to	O
a	O
project	O
,	O
is	O
to	O
first	O
create	O
a	O
personal	O
branch	B-General_Concept
of	O
the	O
repository	O
,	O
independent	O
of	O
the	O
main	O
repository	O
,	O
and	O
later	O
seek	O
to	O
have	O
your	O
changes	O
integrated	O
with	O
it	O
.	O
</s>
<s>
Sites	O
such	O
as	O
GitHub	B-Application
,	O
Bitbucket	B-Protocol
and	O
Launchpad	B-Protocol
provide	O
free	O
DVCS	O
hosting	O
expressly	O
supporting	O
independent	O
branches	O
,	O
such	O
that	O
the	O
technical	O
,	O
social	O
and	O
financial	O
barriers	O
to	O
forking	O
a	O
source	O
code	O
repository	O
are	O
massively	O
reduced	O
,	O
and	O
GitHub	B-Application
uses	O
"	O
fork	B-Language
"	O
as	O
its	O
term	O
for	O
this	O
method	O
of	O
contribution	O
to	O
a	O
project	O
.	O
</s>
<s>
Forks	B-Language
often	O
restart	O
version	O
numbering	O
from	O
0.1	O
or	O
1.0	O
even	O
if	O
the	O
original	O
software	O
was	O
at	O
version	O
3.0	O
,	O
4.0	O
,	O
or	O
5.0	O
.	O
</s>
<s>
MariaDB	B-Application
for	O
MySQL	B-Application
or	O
LibreOffice	B-Application
for	O
OpenOffice.org	B-Application
.	O
</s>
<s>
The	O
BSD	B-Operating_System
licenses	I-Operating_System
permit	O
forks	B-Language
to	O
become	O
proprietary	B-Application
software	I-Application
,	O
and	O
copyleft	B-License
proponents	O
say	O
that	O
commercial	O
incentives	O
thus	O
make	O
proprietisation	O
almost	O
inevitable	O
.	O
</s>
<s>
(	O
Copyleft	B-License
licenses	I-License
can	O
,	O
however	O
,	O
be	O
circumvented	O
via	O
dual-licensing	O
with	O
a	O
proprietary	B-Application
grant	O
in	O
the	O
form	O
of	O
a	O
Contributor	O
License	O
Agreement	O
.	O
)	O
</s>
<s>
Examples	O
include	O
macOS	B-Application
(	O
based	O
on	O
the	O
proprietary	B-Application
NeXTSTEP	B-Application
and	O
the	O
open	O
source	O
FreeBSD	B-Operating_System
)	O
,	O
Cedega	B-General_Concept
and	O
CrossOver	B-Operating_System
(	O
proprietary	B-Application
forks	B-Language
of	O
Wine	B-Application
,	O
though	O
CrossOver	B-Operating_System
tracks	O
Wine	B-Application
and	O
contributes	O
considerably	O
)	O
,	O
EnterpriseDB	O
(	O
a	O
fork	B-Language
of	O
PostgreSQL	B-Application
,	O
adding	O
Oracle	O
compatibility	O
features	O
)	O
,	O
Supported	O
PostgreSQL	B-Application
with	O
their	O
proprietary	B-Application
ESM	O
storage	O
system	O
,	O
and	O
Netezza	O
's	O
proprietary	B-Application
highly	O
scalable	O
derivative	O
of	O
PostgreSQL	B-Application
.	O
</s>
<s>
In	O
proprietary	B-Application
software	I-Application
,	O
the	O
copyright	O
is	O
usually	O
held	O
by	O
the	O
employing	O
entity	O
,	O
not	O
by	O
the	O
individual	O
software	O
developers	O
.	O
</s>
<s>
Proprietary	B-Application
code	O
is	O
thus	O
more	O
commonly	O
forked	O
when	O
the	O
owner	O
needs	O
to	O
develop	O
two	O
or	O
more	O
versions	O
,	O
such	O
as	O
a	O
windowed	O
version	O
and	O
a	O
command	B-Application
line	I-Application
version	O
,	O
or	O
versions	O
for	O
differing	O
operating	O
systems	O
,	O
such	O
as	O
a	O
word	B-General_Concept
processor	I-General_Concept
for	O
IBM	B-Device
PC	I-Device
compatible	O
machines	O
and	O
Macintosh	B-Device
computers	O
.	O
</s>
<s>
Generally	O
,	O
such	O
internal	O
forks	B-Language
will	O
concentrate	O
on	O
having	O
the	O
same	O
look	O
,	O
feel	O
,	O
data	O
format	O
,	O
and	O
behavior	O
between	O
platforms	O
so	O
that	O
a	O
user	O
familiar	O
with	O
one	O
can	O
also	O
be	O
productive	O
or	O
share	O
documents	O
generated	O
on	O
the	O
other	O
.	O
</s>
<s>
This	O
is	O
almost	O
always	O
an	O
economic	O
decision	O
to	O
generate	O
a	O
greater	O
market	O
share	O
and	O
thus	O
pay	O
back	O
the	O
associated	O
extra	O
development	O
costs	O
created	O
by	O
the	O
fork	B-Language
.	O
</s>
<s>
A	O
notable	O
proprietary	B-Application
fork	B-Language
not	O
of	O
this	O
kind	O
is	O
the	O
many	O
varieties	O
of	O
proprietary	B-Application
Unix	B-Application
—	O
almost	O
all	O
derived	O
from	O
AT&T	O
Unix	B-Application
under	O
license	O
and	O
all	O
called	O
"	O
Unix	B-Application
"	O
,	O
but	O
increasingly	O
mutually	O
incompatible	O
.	O
</s>
<s>
See	O
Unix	B-Application
wars	O
.	O
</s>
