What does this concrete mean? Will the whole SOAP API be removed? What'll be the alternative API to access Mantis data with external tools?

No, just that this particular branch does not have a functional SOAP API . The API will not be removed.

The next version of major mantis will possibly have a new webservice api that supports more then just SOAP - hence for the current restructuring of objects the branch doesn't include that nusoap based soap api.

This would be part of a move at looking to use objects more within the code base - so until we've finished tweaking the internal API's, we pulled out the SOAP code.

Don't worry - this issue does not affect any official MantisBT branches. It is in relation to some experimental branches that some of the developers were playing around with. The idea being played with is to rewrite and modernise MantisBT and in the process, improve SOAP functionality and add JSON, REST and any other APIs that may be useful. At this stage it is all pie-in-the-sky and there is nothing to start planning for. If/when something more concrete is decided from this experimentation, it'll be widely advertised on the dev mailing list, blog, etc before any real work is done (and it'll take ages so there will be plenty of notice).

marking this as closed as not to confuse anyone