Opcode's greatest contribution to the MIDI world was probably the Opcode MIDI System, a.k.a OMS (which was later renamed the Open Music System). OMS was a set of system software for the classic MacOS that managed MIDI routing and processing. Read more about The Opcode MIDI System a.k.a OMS
Opcode made MIDI and later audio software for the Macintosh platform in the late 80's and the 90's. Eventually they did release their MIDI sequencing app Vision for Windows as well, but their primary focus was always the Mac. Read more about Opcode Software and Hardware
SQ8L is a soft synth version of Ensoniq's SQ-80 synthesizer. SQ8L's creator, Siegfried Kullmann, states in the readme.txt file that the "L" stand for "Light" and that there will be a commercial "SQ8X" (X for "extended") version. The last we have heard about that however was in 2008, so my advice for not is the enjoy the free synth light SQ8L version as it sounds and works great. I have personally used this under Slackware with dssi and have had no problems. Read more about SQ8L Ensoniq SQ-80 Free Soft Synth
seq24 is an open source remake of the old style MIDI step loop sequencers. If you are a fan of the old style step sequencers (and if you're not, you should be) you owe it to yourself to check out seq24, it's awesome and has a lof of serious fans. You can even buy seq24 shirts from the seq24 website. Read more about seq24 loop step MIDI sequencer
Opcode released their flagship MIDI sequencing software Vision back in 1989 for the Macintosh. Vision was very well received and was on the top of it's game at the time, winning several awards. It was in 1990 however that Opcode gave birth to Opcode Studio Vision.
I have a lots of fond memories of hours upon hours spent in Studio Vision. Studio Vision stood out as the first MIDI sequencer to integrate digital audio recording. It was the first sequencer that i ever owned (software or hardware) and served me well starting back in 1991 on my old Mac IIci. Read more about Opcode Studio Vision MIDI Sequencer for MacOS Classic
I would say that the House of Synth is indeed a great place to get your vintage synthesizers from...I would recommend it even for my mother in law :) Thank for giving me the opportunity to get such a great piece of machinery!!!