Currently, the most famous open source vbscript client side is baleas2.
If you are talking about server side, for example, scripts, the list of options is very long: instant-asp (ib4j-tomcat, java), rbsp (realbasic-server-pages), pbsp (purebasic-server-pages), run-basic ( libertybasicscript) etc. with almost all fully developed vb commercial alternatives.
Regarding the basic Windows-based open source, the basicwebscripting area currently includes maven-sb4j, scriptbasic, and gbs3 (gambas server pages). Then, server side pages may soon become another option in the future (after development to support curl and proxyserver / fastcgi).
You can also try using maven-sb4j for jbasic, jabaco, scriptbasic-japi and yabasic-japi.
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