OpenLink actively supports Progress 8 and 9. OpenLink provides some legacy support for Progress 6 and 7.  

If you must establish a shared memory connection to your Progress database, you must download an agent which matches your Progress version and release. For instance, Progress 83A database agents permit shared memory connections to Progress 83A databases. Progress 83B agents do not. Alternatively, Unix users may relink a database agent against their backend databases. Relinking eradicates agent-database incompatibilities which prohibit shared memory connections.  

If you want to establish a sockets connection to your Progress database, you may use any database agent which shares the same major version as your Progress database. For instance, you may use any Progress 9 agent to establish a sockets connection to a Progress 91A database. However, you may not use a Progress 8 agent to establish the same connection.