Hi,Your best option is to check out eComStation. eComStation is an OEM version of IBM's OS/2 Warp 4 MCP (Version 4.52 - the latest version from IBM) with a new installer, updated device drivers and some additional utilities and enhancements. It continues to receive regular updates and a new version is slated to be released this year (currently the new version is in beta testing). It is available at:
http://www.ecomstation.com/
There is also an option to download a free bootable demo CD from that website so you can give it a try and see what it looks like before purchasing it.
If you're looking to buy a license for Warp 4 direct from IBM, you're going to have a difficult time. IBM no longer sells OS/2 Warp to customers directly as they have withdrawn the product from active marketing. This means that unless you have an OS/2 service contract or an OEM agreement already in place with IBM, you won't be able to purchase a copy or license from them (at least this is my understanding). You can read more about the current status of OS/2 within IBM at:
http://www-306.ibm.com/software/os/warp/
If you want the original '96 release of Warp 4 (ie, Version 4.00), your best bet is eBay. Usually there are a few copies of Warp 4 on eBay. But be warned that going this route you wouldn't get a copy containing the latest updates and device drivers, so it could take you a bit of work to get it installed and updated to a point that it'll run well on today's systems (mind you, it isn't impossible to update the '96 V4.00 release of Warp and get it running well, in fact this topic has been covered on a few different threads on the os2world forums, but it just takes work, persistance, and know-how to do).
Hope this helps