As part of exp-run in bug 223922 this port was found to break on Boost update. If the issue won't disappear on its own by Boost release I plan to mark the port as BROKEN. Can you check with upstream maintainer or help with a fix?
$ fetch -qo- 'https://reviews.freebsd.org/D13279?download=true' | patch -Efsp0 -d /usr/ports
$ make all deinstall install clean -C/usr/ports/devel/boost-libs
$ make -C/usr/ports/games/spring
rts/System/FileSystem/Archives/SevenZipArchive.cpp:129:52: error: no member named 'get_system_category' in namespace 'boost::system'
boost::system::error_code e(wres, boost::system::get_system_category());
A commit references this bug:
Date: Sat Mar 3 22:40:57 UTC 2018
New revision: 463538
games/spring: unbreak with boost 1.66
Obtained from: upstream
Approved by: portmgr blanket
Is this port really maintained? Spring had 6 releases after 98.0.