I believe NLS themselves should do the translation:
http://www.maanmittauslaitos.fi/en/opendata
http://www.maanmittauslaitos.fi/en/NLS_open_data_licence_version1_20120501

It is “open” but there are some restrictions in 2.2

  • mention the name of the Licensor, the name of the dataset(s) and the time when the National Land Survey has delivered the dataset(s)
    and
  • require third parties to provide the same information when granting rights to copies of dataset(s) or products and services containing such data

These two are restricting the use of data in OSM unless some actions are agreed with NLS and also committed. There has been some discussion about how to tackle these two, though.

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