In a perfect world were everybody works according to the standards there shouldn't be any differences between all those database types.
Unfortunately each database type uses a different query dialect, for instance mssql uses  to escape table names and aliases, oracle allows " to escape table names but not for an alias and the 'AS' statement isn't allowed for tables.
I can continue to sum up all differences for a while, but basically each database has some small differences compared to the standard and each other.
Yes it should be easy to support Progress as additional database type, however it has never been tested. And each of the databases mentioned in the modeler have been tested.
You can easily add Progress and test if it works...
This is the info you need to find out first:
- jdbc driver class name - jdbc connection string - escape character for tables and aliases
Add Progress the database type enumeration deploy the project, open in a Java editor the class: databasereplication.implementation.DatabaseConnector.
Around line 80, add Progress to the switch statement and determine the connection string for Progress.
Around line 119, add Progress to the enum and add the driver class, the escape character here.
If there aren't any special cases in the dialect of progress this should mean that progress is working already and you could import the tables. However there could also be a lot of minor differences in the Progress dialect, which could trigger some exceptions.
Further down in this class (line 159 till the end) the select, join and from statements are created. So if there are any differences in the query dialect you can add the special cases here.
If you've got Progress to work please let us know what you had to change in the class so we can add those changes to the module and support one more database type.
Don't you mean "Postgres"? If so, yes, and it's easy to google.
I use the database replicator, of course, but according to the documentation it supports MSSQL, Postgresql and Oracle.
Progress is another system http://en.wikipedia.org/wiki/Progress_Software
It is available as JDBC driver
Maybe you could find some info @ Postgresql
or in the wiki