<s>
SkyOS	B-Application
(	O
Sky	O
Operating	B-General_Concept
System	I-General_Concept
)	O
is	O
a	O
discontinued	O
prototype	O
commercial	O
,	O
proprietary	B-Application
,	O
graphical	O
desktop	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
written	O
for	O
the	O
x86	B-Operating_System
computer	B-General_Concept
architecture	I-General_Concept
.	O
</s>
<s>
In	O
August	O
2013	O
,	O
developer	O
Robert	O
Szeleney	O
announced	O
the	O
release	O
of	O
a	O
public	O
beta	O
on	O
the	O
SkyOS	B-Application
website	O
.	O
</s>
<s>
This	O
allows	O
public	O
users	O
to	O
download	O
a	O
Live	O
CD	O
of	O
the	O
SkyOS	B-Application
operating	B-General_Concept
system	I-General_Concept
,	O
for	O
testing	O
and	O
to	O
optionally	O
install	O
the	O
system	O
.	O
</s>
<s>
Starting	O
with	O
beta	O
development	O
of	O
SkyOS	B-Application
5	O
in	O
2003	O
,	O
users	O
were	O
required	O
to	O
pay	O
US$30	O
to	O
get	O
access	O
to	O
beta	O
releases	O
.	O
</s>
<s>
SkyOS	B-Application
adapted	O
new	O
filesystem	B-Application
SkyFS	O
based	O
on	O
OpenBFS	B-Language
in	O
2004	O
and	O
its	O
graphics	O
subsystem	O
was	O
improved	O
in	O
2006	O
with	O
support	O
for	O
desktop	B-Operating_System
compositing	I-Operating_System
including	O
double	O
buffering	O
and	O
transparency	B-Algorithm
.	O
</s>
<s>
As	O
the	O
OS	O
was	O
mainly	O
the	O
work	O
of	O
one	O
man	O
,	O
Robert	O
Szeleney	O
,	O
there	O
was	O
increasing	O
difficulty	O
to	O
add	O
new	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
Considering	O
lack	O
of	O
development	O
under	O
Robert	O
Szeleney	O
,	O
going	O
open	B-License
source	I-License
was	O
viewed	O
by	O
the	O
tech	O
press	O
as	O
the	O
best	O
option	O
for	O
SkyOS	B-Application
.	O
</s>
<s>
Although	O
Szeleney	O
tried	O
to	O
bypass	O
the	O
lack	O
of	O
drivers	O
by	O
using	O
a	O
new	O
kernel	O
based	O
on	O
Linux	B-Application
or	O
NetBSD	B-Device
,	O
and	O
reported	O
some	O
progress	O
in	O
this	O
regard	O
,	O
development	O
has	O
not	O
resumed	O
.	O
</s>
<s>
SkyOS	B-Application
website	O
disappeared	O
in	O
2013	O
and	O
final	O
public	O
build	O
from	O
August	O
2008	O
was	O
released	O
for	O
free	O
shortly	O
thereafter	O
.	O
</s>
<s>
SkyOS	B-Application
is	O
a	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
with	O
a	O
monolithic	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
The	O
OS	O
supports	O
multiple	B-Operating_System
users	I-Operating_System
and	O
symmetric	B-Operating_System
multiprocessing	I-Operating_System
.	O
</s>
<s>
SkyOS	B-Application
has	O
an	O
integrated	O
graphics	O
subsystem	O
with	O
support	O
for	O
desktop	B-Operating_System
compositing	I-Operating_System
including	O
double	O
buffering	O
and	O
transparency	B-Algorithm
.	O
</s>
<s>
SkyOS	B-Application
GUI	O
also	O
allows	O
system-wide	O
mouse	O
gestures	O
.	O
</s>
<s>
SkyFS	O
is	O
a	O
fork	B-Application
of	O
the	O
OpenBFS	B-Language
filesystem	B-Application
.	O
</s>
<s>
SkyOS	B-Application
can	O
also	O
be	O
run	O
from	O
the	O
following	O
filesystems	B-Application
:	O
</s>
<s>
SkyOS	B-Application
offers	O
real-time	O
file	O
content	O
query	O
searches	O
with	O
multiple	O
keywords	O
(	O
comparable	O
to	O
Beagle	B-Language
in	O
Linux	B-Application
or	O
Spotlight	B-Application
in	O
macOS	B-Application
)	O
,	O
including	O
indexing	B-Application
of	O
files	O
and	O
programs	O
.	O
</s>
<s>
Most	O
command-line	O
applications	O
that	O
were	O
written	O
to	O
be	O
compiled	O
with	O
the	O
GNU	B-Application
Toolchain	I-Application
can	O
be	O
ported	O
to	O
SkyOS	B-Application
with	O
little	O
or	O
no	O
modification	O
.	O
</s>
<s>
SkyOS	B-Application
contains	O
several	O
frameworks	O
for	O
creating	O
applications	O
(	O
including	O
Mono	B-Application
port	O
)	O
.	O
</s>
<s>
Ported	O
applications	O
include	O
Mozilla	B-Application
Firefox	I-Application
,	O
Mozilla	B-Application
Thunderbird	I-Application
,	O
Nvu	B-General_Concept
,	O
GIMP	B-Application
and	O
AbiWord	B-Language
.	O
</s>
<s>
There	O
was	O
also	O
a	O
monetary	O
incentive	O
for	O
porting	O
applications	O
as	O
the	O
SkyOS	B-Application
community	O
voted	O
for	O
desired	O
programs	O
and	O
then	O
supported	O
developers	O
with	O
donations	O
.	O
</s>
<s>
Although	O
SkyOS	B-Application
includes	O
many	O
interesting	O
features	O
,	O
limited	O
application	O
and	O
hardware	O
support	O
are	O
among	O
its	O
weaknesses	O
(	O
e.g.	O
</s>
<s>
only	O
a	O
few	O
graphics	B-Device
cards	I-Device
allow	O
2D	O
acceleration	O
)	O
.	O
</s>
<s>
Apart	O
from	O
a	O
short	O
early	O
open	B-License
source	I-License
time	O
period	O
,	O
the	O
OS	O
had	O
a	O
proprietary	B-Application
licence	I-Application
with	O
a	O
commercial	O
model	O
based	O
on	O
paid	O
beta-testing	O
.	O
</s>
<s>
This	O
led	O
to	O
some	O
controversy	O
as	O
SkyOS	B-Application
developers	O
were	O
accused	O
of	O
unauthorized	O
use	O
of	O
open	B-License
source	I-License
software	O
.	O
</s>
