  [Context] Open Source Software (OSS) is nowadays used and integrated in most
of the commercial products. However, the selection of OSS projects for
integration is not a simple process, mainly due to a of lack of clear selection
models and lack of information from the OSS portals.
  [Objective] We investigated the current factors and measures that
practitioners are currently considering when selecting OSS, the source of
information and portals that can be used to assess the factors, and the
possibility to automatically get this information with APIs. [Method] We
elicited the factors and the measures adopted to assess and compare OSS
performing a survey among 23 experienced developers who often integrate OSS in
the software they develop. Moreover, we investigated the APIs of the portals
adopted to assess OSS extracting information for the most starred 100K projects
in GitHub.
  [Result] We identified a set consisting of 8 main factors and 74 sub-factors,
together with 170 related metrics that companies can use to select OSS to be
integrated in their software projects. Unexpectedly, only a small part of the
factors can be evaluated automatically, and out of 170 metrics, only 40 are
available, of which only 22 returned information for all the 100K projects.
  [Conclusion.] OSS selection can be partially automated, by extracting the
information needed for the selection from portal APIs. OSS producers can
benefit from our results by checking if they are providing all the information
commonly required by potential adopters. Developers can benefit from our
results, using the list of factors we selected as a checklist during the
selection of OSS, or using the APIs we developed to automatically extract the
data from OSS projects.
