PhysTechSoft was formed in 1991 in Moscow, Russia by graduates and members of MIPT, informally known as PhysTech. In the end of 1993, PhysTechSoft released first commercially available PTS-DOS as PTS-DOS v6.4 (version numbering obviously seems to follow versions of MS-DOS, as Microsoft released MS-DOS 6.2 in November 1993).
Some programmers who left PhysTechSoft in 1995 founded Paragon Software GmbH, took source code with them and released their own version named PTS-DOS v6.51CD. According to official PhysTechSoft announcements, these programmers violate both copyright laws and Russian military laws, as PTS-DOS was developed in close relationship with Russian military and thus may be subject to military secret.
PhysTechSoft continued development on their own and released PTS-DOS v6.6 somewhere in between and presented PTS-DOS v6.65 at CeBIT exhibition in 1997. Next version from PhysTechSoft, formally PTS/DOS Extended Version 6.70 was labelled PTS-DOS 2000 and is still being distributed as a last 16-bit PTS-DOS system, as of 2007.
Paragon continued PTS-DOS line and released Paragon DOS Pro 2000 (also known and labelled in some places as PTS/DOS Pro 2000). According to Paragon, this was the last version and all development since then ceased. Moreover, this release contained bundled source code of older PTS-DOS v6.51.
PTS-DOS is certified by Russian Ministry of Defence.