During Yeshiva I remember some bochrim made a point of not putting the Jastrow dictionary on top of sefarim, and would often talk about how it does not have kedusha because it was written by an apikores. Was Marcus Jastrow really an apikores?
From "Were Our Mouths Filled with Song": Studies in Liberal Jewish Liturgy by Eric L. Friedland.
Jastrow's Reform principles- the degree and definition of his Reform- are precisely defined in Antwort an Herrn I. M. Wise (1867) in the form of a syllabus errorum...:
- I am for any reform that is able to influence the moral enhancement of the Jews.
- I am against any kind of reform that issues out of a mere desire toward assimilation or grasping after innovation without its being a mean toward moral elevation.
- I am for any reform that is compatible with the spirit of Judaism.
- I am against any reform that denies this spirit.
- I am for any reform that confers the outer appearance of Jewish thought-content with beauty and worth.
- I am against any reform that ascribes all worth to outer appearance.
- I am for any reform that links itself with the historical development of Judaism.
- I am against any reform that severs its connection with the past.
13 . I am for any reform that is, without strain, consistent with the Bible and its oldest traditional interpretation, as set down by the Talmud.
14 . I am against any reform that arbitrarily creates new interpretations, inasmuch as I know I cannot do without the traditional guide in the practical implementation of the biblical commandments.
15 . I am for any reform that removes the old-fashioned prayers that came into being during the Middle Ages.
16 . I am against any reform that touches or alters the oldest portions of the prayers.
Now, nothing here is particularly heretical in the narrow sense of the term. I mean, there are wrong ideas, indeed disastrous ideas that as bad as they are, are not technically heretical.
It's quite clear that Jastrow would be very disappointed with today's Reform and Conservative Judaism. Orthodoxy has survived and thrived in the modern world. It could be, that given Orthodoxy's latter day success in living in the modern world, that Jastrow would not call for any reforms would he be alive today.