I had a site recently try this and claimed it caused major problems because Moab would try to start jobs there. I tested against this here is what I found. (Version: moab server 8.1.2)
This looks like a non-issue unless you purposely try to tie jobs to the non-licensed nodes. Either the customer was mistaken in what he was seeing OR we was not accurately assessing the information. What I think he might have been doing is he placed all his new nodes in a specific class and then submitted to that class so I tested that as well and the jobs automatically cancel once they were considered for the priority reservation.
[nburton@ibm08 ~]$ mdiag -n
compute node summary
Name State Procs Memory Opsys
ibm10.ac Busy 0:40 7823:7823 linux
ibm11.ac Busy 0:40 7823:7823 linux
ibm13.ac --- 0:0 0:0 linux
ibm14.ac --- 0:0 0:0 linux
----- --- 0:80 15646:15646 -----
Total Nodes: 4 (Active: 2 Idle: 0 Down: 2)
[nburton@ibm08 ~]$ showq
active jobs------------------------
JOBID USERNAME STATE PROCS REMAINING STARTTIME
415 nburton Running 40 00:59:51 Fri Aug 5 10:45:22
416 nburton Running 40 00:59:52 Fri Aug 5 10:45:23
2 active jobs 80 of 80 processors in use by local jobs (100.00%)
2 of 2 nodes active (100.00%)
eligible jobs----------------------
JOBID USERNAME STATE PROCS WCLIMIT QUEUETIME
417 nburton Idle 40 1:00:00 Fri Aug 5 10:45:29
418 nburton Idle 40 1:00:00 Fri Aug 5 10:45:29
2 eligible jobs
blocked jobs-----------------------
JOBID USERNAME STATE PROCS WCLIMIT QUEUETIME
0 blocked jobs
Total jobs: 4
(Example of Auto Cancellation when locked into a class on the violating nodes)
[nburton@ibm08 ~]$ echo sleep 100 | msub -l nodes=1:ppn=40 -q test -l walltime=300
422
[nburton@ibm08 ~]$ showq
active jobs------------------------
JOBID USERNAME STATE PROCS REMAINING STARTTIME
0 active jobs 0 of 80 processors in use by local jobs (0.00%)
0 of 2 nodes active (0.00%)
eligible jobs----------------------
JOBID USERNAME STATE PROCS WCLIMIT QUEUETIME
422 nburton Canceling 40 00:05:00 Fri Aug 5 10:50:54
1 eligible job
blocked jobs-----------------------
JOBID USERNAME STATE PROCS WCLIMIT QUEUETIME
0 blocked jobs
Total job: 1