The sections that follow are for historical interest only, or perhaps for people on very old versions of OSR5 or UW7.
jls@sco.com

Here's the long answer.

There are four commercial sources for the Standard Template Library: 
     Modena,      ( modena@netcom.com )
     Rogue Wave   ( http://www.roguewave.com ),
     Dinkumware   ( http://www.dinkumware.com )
 and 
     ObjectSpace  (http://www.objectspace.com/toolkits/ ).

These vendors generally sell the STL either on an OEM basis to compiler vendors,
or as part of large site licenses. In other words, it's hard to get a single
user license, especially for SCO platforms. 

There is also an up-to-date, public domain version of STL: 

     Silicon Graphics  ( http://www.sgi.com/Technology/STL )

This is the best bet for using on SCO platforms. We have a packaged version
of it for UDK C++; see the "short answer" above.

Note: As of July 1997, the ObjectSpace STL is now also available free for
commercial use. However the ObjectSpace download page only offers it in packaged
form and for only a few platforms. The Solaris 2.5 and Windows 95 versions have
been downloaded and unpacked but they are tailored for the compilers on those
platforms and efforts to build them show that it would be a lot of work to get
them to compile with the UDK C++ compiler (partly because every C++ compiler
supports different new features right now, and partly because the
auto-configuration tool they use is not included in these distributions). 
I can't unpack their MIPS/Irix version, which is the only one compiled 
against an EDG-based compiler, because their install tool is an executable 
program.  ObjectSpace has told me in e-mail that they have no plans to 
distribute a source code only, configuration-tool-included version of their 
STL, so I can't be too hopeful of making use of it on SCO platforms

In addition, versions 2.6.2 and later of libg++ (the GNU C++ library) include at
least a part of the STL that works with GNU C++. However as of egcs libg++ 
has been trashed and has been replaced by the SGI version.

There is also the original public domain version from Hewlett-Packard that is
still available, but it is inferior to the current one from SGI, from which it
is based. (Alex Stepanov, the inventor of STL, now works for SGI.)



OpenServer and UnixWare 2.x C++

The native OpenServer 5.0 C++ compiler is Cfront-based, and thus will have an
impossible time compiling most STLs. At one time, ObjectSpace said that their
STL had been specially modified to compile with Cfront, in which case OSR5 C++
should work. Don't know if this is still the case. 

We have not recently tested any of the STLs against the native UnixWare 2.0 or 2.1 C++
compilers. At one time they all could build, but the STL code may now be assuming more
advanced compiler features. 

In both cases, you're *much* better off moving to the UDK, because it supports many more of
the advanced template features that STL relies upon and takes advantage of.