Artist J.B. Schweitz, born Indonesia, worked in Netherlands Antilles,
in collection of Museum of Modern Art - last heard of living in the
Netherlands, is he still working, and is his art available?

According to  

http://zoeken.bibliotheek.nl/asp/mlPanel.asp?recpos=0&hrec=262656376

Schweitz died in 1982.

As my previous comment only resulted in a "session timed out" message,
I'll now try to provide a more detailed account.

A catalogue "De Wereld van J.B. Schweitz" was published in 1983
(co-author: Elly Neumann- Baumert):
http://members.tripod.com/~gardenculture/WEB/elly.html

You can search for details of this publication by going to
http://zoeken.bibliotheek.nl/index.html

Entering "De Wereld van J.B. Schweitz" and clicking on "zoek" you will
see "De wereld van Johan Bernhard Schweitz". Clicking on the title
will open a new window giving the following details concerning the
publication:
"Monografie over de in Indonesië geboren Antilliaans/Nederlandse
kunstschilder (1937-1982)"

A short review ("Korte bespreking") is available when clicking on
"Meer informatie".

I don't know if "1937-1982" refers to a particular period of Schweitz
as a painter, or if he was born in 1937 and died in 1982 (as I
presumed in my previous comment).