A version of Ersatz-11 is available for OS/2 or eComStation. While E11 customers haven't exactly been clamoring for this version, it exists and D Bit plans to continue supporting OS/2 in future releases of E11. The OS/2 version has reduced device support compared to other versions but it runs quite well. OS/2 handles multithreading a bit more naturally than Windows does, and is an excellent fit to E11's internal structure.
Pricing is the same as the Windows version, including the upgrade policy for existing DOS or Linux customers.
There is a Demo version of E11 which may be used for a 30-day commercial evaluation (no limit on hobbyist use). The manual for the Demo version is included in the self-extracting archive, or it may be downloaded separately here.