Two years ago we had and old version of jbpm integrated into OpenKM and we decided to separated the engine from the openkm core. After several years we have arrived at the conclusion is better working on a wrapper rather be integrated on an unique BPM solution. At same time we have been working on Bonita Soft integration
http://docs.openkm.com/kcenter/view/bwc/
Take the next opinion, as my personal opinion after several years working on this kind of scenarios ( BPM and DMS working together). From my point of view one of two applications should be considered the master and the second an slave. If you really have an intensive use of workflows, should think on an scenario where you really only access to BPM engine ( screens, etc... ) and where the DMS is used only as a container. When you have few workflows ( you really do not have WF scenario ), then is good approach use DMS and some minimal integration with thirdparty BPM or integrated engine.
I think almost people thinks that a workflow are several squares linked by lines etc... but in productions environments workflows usually are complex logic what needs a lot of knowledge by the BPM managers ( usually technical staff ). Usually the marketing guys of BPM share slides and videos, where everything seems easy and trivial, but on real scenarios the things changes. During all years we have implemented workflows I still have not seen two similar workflows.
