Operating system name and version: Slackware64-current
Version of smsd: 3.1.14
Smsd installed from: sources with slackbuild script from SBo
Name and model of a modem / phone: HTC desire
Interface: USB

At running smsd with the rc.sms3 start command as root, I get the following message:
Starting SMS Daemon: Cannot open logfile
smsd failed.

If I comment out the logfile specification in rc.sms3 and /etc/smsd.conf, I get the following errors:

Starting SMS Daemon: Spool directory /var/spool/sms/outgoing is not writable.
Incoming directory /var/spool/sms/incoming is not writable.
Checked directory /var/spool/sms/checked is not writable.
Infofile /var/run/smsd.working cannot be created: Permission denied
Shell /bin/sh testing failed: Cannot create test script file.
There was 5 major problems found.
Cannot start. See the log file for details.
smsd failed.

I'm surprised if these files need to be manually created.
I can't find any info on this issue.

Is this problem still active?

I do not know about slackbuild, but perhaps there are user and group settings used. This may mean that even if command was executed as root, smsd continues with limited permissions.

All directories must be manually created, and permissions must be manually adjusted.