The Software keyboard started about 1999 with a prototype from Creamware (Now taken over by Sonic-Core http://www.sonic-core.net/de/home/home.html ) in Germany; http://www.harmony-central.com/Events/MusikMesse00/CreamWare/CreamWare-StageFrame.html
This was subsequently taken up by Wersi and launched in 2000/1 as the OAS system.
Neko (I Think) and TMS followed later, with Lionstracs coming in about 2003/4.
In addition although not software, Bohm http://www.keyswerk.de/ also produce an arranger module.
http://www.openlabs.com/products.html
http://www.lionstracs.com/store/index.php
http://www.wersi.net/
http://www.tornado-music.de/

Regards

Bill