Several older modules from the XBS (XOOPS Business Systems) series have been updated for PHP 7.1. Still a lot of bugs, but feel free to help with fixing them:

• XBS Tags:https://github.com/mambax7/xbs_tags
• XBS Small Accounts: https://github.com/mambax7/xbs_sacc
• XBS Code Data Management: https://github.com/mambax7/xbs_cdm
• XBS VAT: https://github.com/mambax7/xbs_vat
• XBS Log: https://github.com/mambax7/xbs_log
• XBS ModGen: https://github.com/mambax7/xbs_modgen 

More info about some of the modules:

https://xoops.org/modules/repository/singlefile.php?cid=19&lid=1660

https://xoops.org/modules/repository/singlefile.php?cid=19&lid=1658

https://xoops.org/modules/repository/singlefile.php?cid=19&lid=1662

https://xoops.org/modules/news/article.php?storyid=3226

https://xoops.org/modules/news/article.php?storyid=2973