This was my experience:
1. install OPA. Get surprised by the AGPL license because the main page mentions that it can be used to develop closed source apps.
2. git clone OPAcman.
3. run make, fail. Read error message (in color, with a little unicode "flag" symbol right where the error is!)
4. change makefile to use --parser classic, also fails
5. hack off score.opa because --parser classic database directives are irrevocably broken and I can't be arsed to figure out the new syntax, also patch opacman.opa with a stubbed out Score object.
6. Run make, get ocaml errors: Error: This expression has type Bsl_init_.CR.t = QmlClosureRuntime.t but an expression was expected of type QmlFlatServerLib.record = ServerLib.ty_record
7. Take a look at some of the ml code generated
let _v686_const = ((Obj.magic) (((QmlFlatServerLib.unsafe_init_static) ([| (((Obj.repr) (( (* ["label" ; "ty"] ) Link_opacman_001._v5_shared_vtable)))) ; (((Obj.repr) (None))) ; (((Obj.repr) (Link_opacman_002._v226_const))) ; (((Obj.repr) (_v685_const))) |])))) let _v687_const = ((Obj.magic) (((QmlFlatServerLib.unsafe_init_static) ([| (((Obj.repr) (( ( ["hd" ; "tl"] *) Link_opacman_001._v6_shared_vtable)))) ; (((Obj.repr) (None))) ; (((Obj.repr) (_v686_const))) ; (((Obj.repr) (Link_opacman_001._v8_const))) |]))))
8. Run AWAY.