Crosswords is played by the same rules as a famous word-formation board game. (This site's policies prohibit my mentioning its name.) Crosswords supports games between from one to four human or robot players, in most European languages via downloadable dictionaries, and between smartphones and tablets over the wireless network, Bluetooth, or using SMS/text messages. Crosswords is free/open source software, and has no annoying ads.
In fact, my Friends say I should call it Words Without Ads.
You may wonder why Crosswords requires so many permissions. Here are the ones you're most likely to question:
* Receive/send SMS messages
If, and only if, you have explicitly enabled the "Allow games via SMS" feature, Crosswords lets you exchange moves transparently via SMS so you don't require a server. The ability to send and receive SMS messages is required for this (even though the type of SMS messages Crosswords uses, "data" messages, does not show up in the Messaging app.) If you do not enable this feature Crosswords will not use SMS-related permissions.
* Read call log/contacts
Again, these permissions are used only if you explicitly enable play via SMS. They allow Crosswords to let you lookup the phone number of someone to invite/challenge.
* Run at startup
If you are playing games via the internet/relay and don't have "Google Cloud Messaging" enabled then periodically Crosswords checks to see if there are any moves waiting for you. Without this permission it could not start checking after you rebooted your phone until you actually started it, which not everybody thinks to do.
* Prevent phone from sleeping
There is an optional setting, disabled by default, that keeps the screen on for a longer period. It was requested by users who found the board going dark while they were studying it. If you do not enable this setting this permission is not used.
Crosswords is rated for mature audiences because very very rarely the robot will play a "nasty" word.
*** Resources ***
You can view or download the source code for CrossWords here: http://xwords.sourceforge.net/source.php
Report bugs or request features here: https://sourceforge.net/p/xwords/_list/tickets?source=navbar
Help with translations here: https://hosted.weblate.org/projects/xwords/android/
Author: Eric House
Market link: org.eehouse.android.xw4
Web site: http://xwords.sf.net/android.php
Market downloads: 50,000-250,000
Market rating: 3.6 / 5.0