Yes. The only requirement is that the client library being used must match the version of the server.
For example, you may have isCOBOL 2021R1 and c-treeRTG 11.9 running on a machine and you want to also run isCOBOL 2022R1 with the same c-treeRTG.
Then you must use the ctree.dll on Windows or libctree.so on UNIX/Linux from the isCOBOL2021R1/bin or native/lib directory with the isCOBOL 2022R1 version.

For example, you can copy /isCOBOL_SDK2021R1/native/lib/libctree.so to your /isCOBOL_SDK2022R1/native/lib directory. Or in Windows copy the isCOBOL_SDK2021R1/bin/ctree.dll file to isCOBOL_SDK2022R1/bin.

Another way to look at this is that on UNIX or Linux, the libctree.so from the isCOBOL 2021R1 version must be in the LD_LIBRARY_PATH, LIBPATH, etc. when running isCOBOL 2022R1.
On Windows the ctree.dll from the isCOBOL 2021R1 version must be the first ctree.dll in the Windows search path when running isCOBOL 2022R1

1. Where do I get additional information about file status 9D?
2. How do I set up c-tree client/server file access?
3. Why do I get Internal error 19:133:0 when using c-treeRTG?
4. Does c-treeRTG support live backup (without needing to get users off the system)?
5. How do I configure remote file paths when using c-treeACE?
6. Do you have a simple test program to see if c-treeRTG is working?
7. To use encryption do I need to set the c-tree config variable before I run ISMIGRATE?
8. Why do I get the error message "faircom.rtg.CtreeEnv.ct_config2(IJJ[Ljava/lang/String;)J" when using c-treeRTG?
9. Why do I get 'ct_init ERROR 19:530:0' trying to work with the c-tree Server?
10. Can I use COBFILEIO to give access to my c-tree files to a Java program?