Today, I released a new version of scikit-survival. This release adds support for the latest version of scikit-learn (0.19) and pandas (0.21). In turn, support for Python 3.4, scikit-learn 0.18 and pandas 0.18 has been dropped.
Many people are confused about the meaning of predictions. Often, they assume that predictions of a survival model should always be non-negative since the input is the time to an event. However, this not always the case. In general, predictions are risk scores of arbitrary scale. In particular, survival models usually do not predict the exact time of an event, but the relative order of events. If samples are ordered according to their predicted risk score (in ascending order), one obtains the sequence of events, as predicted by the model. A more detailed explanation is available in the Understanding Predictions in Survival Analysis section of the documentation.