Shameless plug: we are working on a javascript solution.

XLSX/XLSM/XLSB reader/writer: https://github.com/SheetJS/js-xlsx

XLS(BIFF8)/XML(2003-4) reader: https://github.com/SheetJS/js-xls

In-browser reader demo: http://oss.sheetjs.com/

In-browser writer demo: http://tokuhirom.github.io/js-xlsx-demo/

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Some other alternatives:

Python xlrd https://github.com/python-excel/xlrd , xlwt https://github.com/python-excel/xlwt , XlsxWriter https://github.com/jmcnamara/XlsxWriter

Java POI https://poi.apache.org/

I don't see any reason why it would be Windows only. All the code appears to be spec-compliant C# that doesn't use P/Invoke to call native modules or rely on C++/CLI. The only sticking point I see is the PowerShell script, and that's pretty trivial to replace since it's just a build script (you could use xbuild/msbuild, since mono supports that, or just use make)

I like that MS is attempting to take a big step into FOSS but having dependencies on their OS and their build environment is reason enough for me to dismiss this stuff. Thanks for generating some interest in the truly free libs out there.

In python, I've had great luck with XlsxWriter

http://xlsxwriter.readthedocs.org/

Make a html, embed the images in base64 using mhtifier.py, and rename the html as doc. Word will open it without problems.

Further instructions:

http://sebsauvage.net/wiki/doku.php?id=word_document_generat...

For Lua there is xlsxwriter:

https://github.com/jmcnamara/xlsxwriter.lua