I downloaded Codesys and then contacted tech support to walk me through connecting to the BL20. The guy I talked to which was supposed to be there software guru. Said he would have to call me back. When he did, he walk me through the software to a point of trying to connect. Then he said that the program might be locked by the developer. We went through some more steps. Then he said I couldn't see the program with the software??? After that I was more confused then before.
I am guessing and will assume he took you through the steps of File->Open->PLC to try to upload the source code. If that failed, then the programmer did not download the source. I find this mostly happens because many CodeSys users do not know the Source Download feature exists and of course sometimes it is because there are the programmers that write "magic code" they do not want anyone else to see. So you end up with something equivalent to a password protected program in an AB PLC.
Personally if it were me, I wouldn't be so quick to dump the BL20, but instead give it a try at writing a new program in CodeSys. When coming from AB, there is a little bit of a learning curve, but I find CodeSys knowledge valuable because most plants I go into now has at least one Codesys based controller whether it's Turck, Wago, Bosch, Beckhoff, Eaton, etc. So it's kind of a bonus that you learn programming for one controller and then you immediately know how to program a large number of different PLCs.
There again this is just me personally, but after I sat down and learned CodeSys, I find that when I go back to AB I am missing all of the tools and features, so it takes about twice as long to write an equivalent program with an AB controller. Don't get me wrong, I like AB PLCs, they have many strengths, but when it comes to programming I think CodeSys is a much more powerful programming environment.