In reply to
Posting this in a new thread because all old threads have been closed.. don't know what's up with that

Anyway, I can't build it.
It looks like it's based on an old Proton version, maybe a year old. I ran into the same problem that was fixed back then:

After doing that, when I build I get 30 duplicate class errors.
[javac] C:\Users\vi-karelc.VI\Desktop\proton_sdk_source-master\RT3DApp\android\temp_final_src\com\rt3dapp\util\ error: duplicate class: com.rtsoft.rt3dapp.util.Base64DecoderException
[javac] public class Base64DecoderException extends Exception {
[javac]        ^
[javac] Note: Some input files use or override a deprecated API.
[javac] Note: Recompile with -Xlint:deprecation for details.
[javac] 30 errors

C:\Users\vi-karelc.VI\Desktop\proton_sdk_source-master\RT3DApp\android\build.xml:130: The following error occurred while executing this line:
C:\Users\vi-karelc.VI\Desktop\proton_sdk_source-master\RT3DApp\android\build.xml:154: Compile failed; see the compiler error output for details.